Antifoggants for formaldehydehardened photographic layers



4 7 type of sensitization. o o

that photographic silver halide emu1-.'.

. formaldehyde as a hardener.

United States Patent 3,128,185 ANTIFOGGANTS FOR- FORMALDEHYDE- HARDENED PHOTOGRAPHIC LAYERS Charles A. Goffe, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Jan. 25, 1960, Ser. No. 4,186

13 Claims. (Cl. 96-108) This invention relates to photographic layers, and more particularly, photographic silverhalide emulsion layers which have been chemically sensitized and treated with formaldehyde as a hardener.

It is known that the sensitivity of photographic silver halide emulsions can-be increased by 'several methods,

including spectral-sensitization and chemicalsen'sitization. In spectralor opticalsensitization, the optical range of sensitivity. is increased, while this is generally not the case in chemical sensitization. The present invention is concerned primarily with chemical sensitization. of. photographic elements containing layers hardened by treatment with formaldehyde. A

Chemical sensitization of silver halide emulsions results in an increase in sensitivity to visibl'elight, generally with little or no change in grain-size distribution or in spectral sensitivity. Several difierent'types 'ofchemical sensitization are known. Oneof the more common types is sulfur sensitization, silver halide emulsions with a'labile sulfur compound and the possible formation of silver sulfide specks in or on the silver halide grain. Another type ofchemical sensitization is gold sensitization, which involves treatment of 7 silver halide emulsions with a gold compound or' salt. Generally, gold sensitization and sulfur sensitization-are 1 additive, i.e., the-sensitizing effects of one type of sensitization do not interfere with and can be added to the other While it is known sions can be simultaneously sensitized bysulfur sensitization and g'old'sensitization, difficulty frequently arises 7 etc.

-My invention. is not confined to any particular sulfur,

, 3,120,185 Patented Apr. 7, 1964 halogen-substituted aldehyde-aliphatic carboxylic acids, including mucochloric acid, rn'ucobromic acid, etc., as

. well as their water-solublesalts, including sodium, potassium,-,triethanol-ammonium, pyridinium, morpholinium,

sensitizer or group of sulfur sensitizers, although I have found that. the following are particularly useful inpracticing my invention: allylisothiourea, allylthiourea, allylisothiocyanate, phenylisothiocyanate, phenylthiourea, sodium. thiosulfate, thiocarbanilide, 'thiourea, thiosemicarbazide, thioacetamide, thioformamide, thiobarbituric acid, etc. Such well known sensitizers have been previously described in Sheppard U.S.' Patent 1,574,944,

whichinvol-ves treatment of I in applying this combined sensitization to photographic silver halide emulsions which have been treated with Formaldehyde is one of the more useful hardeners used in photographyand offers considerable advantages over many other hardeners, including mucochloric acid, mucobromic acid, etc. However, when using formaldehyde hardening in conjunction with sulfurand gold-sensitized emulsions, difficulty arises in that the fog levels of the emulsions frequently increase substantially.

The present invention makes possible the combination of gold sensitization and sulfursensitization in photographic emulsions or layers which are hardened by treat.- I

ment with formaldehyde.

It is, accordingly, an object of my invention to provide Ichemically sensitized photographic silver halidev 61111117 sions. Anotherobject -is to provide photographic silver halide emulsions and layers which have been hardened 1 with formaldehyde. Still another object of my invention..is..to provide, a means for using sulfur and gold sensitization 'where photographic emulsions or layers have been treated with formaldehyde. as a hardener, without seriously increasing the fog levels of the emulsions. Other objects'will become apparent from a consideration of' the following description and examples. g According to my invention, I have found that the fog levels of photographic silver halide emulsions or labile sulfur compound and' a gold salt or compound,

- and hardened by treatment with formaldehyde, can be controlled. by treatment with various aldehyde comlayers, which have been chemically sensitized with a i issued March 2, 1926; Sheppard et al. US. Patent 1,623,-

499, issued April'5, 1927; Sheppard et al. US. Patent 2,410,689, issued N0vember'5, 1946, etc.

Gold salts or compounds useful in practicing my in-' vention are also well known to those skilled in the art and comprise auric trichloride, sodium chloroaurate,

potassium chloroaurite, potassium bromaurite, potassium rodoaurrte, potassium iodoaurate, potassium aurithiocyanate, potassium aurichloride, auric sulfate, sodium auric chloride, potassium auric bromide, sodium auric bromide, alkalilmetal aurous thiosulfate, alkali metal aurous sulfite, thioureaauric chloride complex, auric chloride 3 ethyl-5-[ (3-ethyl-2(3H) benzoxazolylidene)- ethylidenelrhodanine addition product (e.g., Damschroder et al. U.S. Pat ent 2,642,361, issued June 16, 1953), etc. Typical gold sensitizers are described in Waller et al. US. Patent 2,399,083, issued April 23,- 1946.

. The formaldehyde can be incorporated directly in the photographic silver halide emulsion, Y or it can be incorporated in a 'contiguous-hydrophilic colloid layer, such'as' an intermediate layer or anovercoating layer comprising gelatin, polyvinyl alcohol, hydrolyzed ccllu- I lose acetate, etc. r

The concentration of sulfur sensitizer and gold sensitizer, as well as the concentration of the formaldehyde, used in my invention can be varied, depending upon the concentration of silver halide, concentration of gelatin, degree of ripening of the silver halide, etc. In general, I have found that from about 1.0 to 10 mg. per mole of silver halide of sulfur sensitizer is adequate for the purposes of my invention. The concentration of gold salt or compound can advantageously vary from about 0.5 to

10.0 mg. per mole of silver halide, although larger- -ifdesired. The amount of amounts can be" employed, formaldehyde in the emulsion should generally be at least about. l'g ram per pound of gelatin and the maximum amount can be asmuch'as about 240 grams, depending upon the effect desired. The concentration of aldehyde antifoggant can likewise vary, although -I have found that generally from about 1 to 240 grams per pound of gelatin is adequate forthe purposes of my invention. The optimum amount of aldehyde antifoggant will vary for a given emulsion and can be determined by running a series of test coatings wherein the time of digestion with the aldehyde antifoggant and temperature of digestion are varied. The following examples will serve to illustrate our invention.

Aldehydes which have been found particularly 3 EXAMPLE 1 A fine-grain, gelatino-silver chlorobromide emulsion containing approximately 120 grams of gelatin per mole of silver was sensitized by the addition of a sulfur sensitizer of the type'shown in Sheppard U.S. Patent 1,623,499 (e.g., allylthiourea) anda water soluble gold salt of the type shown in Waller et al.- US. Patent 2,399,083v (e.g., sodium chloroaurate) and the emulsion two parts as follows: I

(a) 2 g. of formaldehyde/mole of silver halide added.

(1) No further addition. (2) No further addition plus dry overcoat No. 1. (3) No further addition plus dry overcoating No.2. (b) 11.4 g.-of mucochloric acid/mole of silver halide added.

(1) No further addition. v (2) No' further addition plus dry overcoat No. 1. (3) No further. addition plus'dry overcoat No. 2.

Dry overcoat No. 1 was coated'from a' gelatin solution with the addition of-a coating aid, such as'saponin, and formaldehyde hardened. The concentration of gelatin was 123 mg. per square foot and the concentration of form:-

aldehyde was 3.25 mg. per square foot. Dry overcoat No. 2 was coated as described for dry overcoat No. 1, except that the formaldehyde concentration was increased to 52 mg. per square foot.

Coatings were made on-a cellulose acetate support and then dried. Exposure was made in an Eastman Type Ib Sensitometer to a step wedge and the coatings were developed for 2% minutes in a developer containing 17.5 grams of hydr'oquinone, 65 grams of sodium formaldehyde bisulfite, a'bulfer made up of sodium carbonate and-sodium bicarbonate to adjust the pH to about 9.9 and suflicient water to make 1 liter (identified developer A below). After development, the coatings were-then fixed, washed and dried in the usual manner. Separate strips of was in gs were developed for 4 minutes in a developer having the following composition:

These coatings were also fixed, washed and dried. Duplicate coatings were incubated for one week at 120 F. and 50% relative humidity and then processed in developer A for 2% minutes and separate strips developed for 4 minutes in developer D11.' The relative speed,

contrast and-fogfor. the coatings were then measured.v

The results are given in Table I below. The relative speed value is inversely proportional to the exposure required to give a density of about 0.3 above fog.

EXAMPLE 2 I A fine-grain, gelatino silver-chlorobromide emulsion, sulfur and gold sensitized as described in Example 1 and containing 120 grams gelatin per mole of silver, was

divided into six batches and the batches treated as follows:'

a-1 2 g. formal'dehy de/ mole silver added.

d-2.-2 g. formaldehyde/mole silver plus 11 .4 g. muco- I chloric acid added.

a-3.-2 g. formaldehyde/mole silver added, held 10 minutes at 40C. then 11.4 g. mucochloric acid/mole silver was added.

' b-1.--11.-4'g. mucochloric acid added.

b-2.l1.4-g. mucochloric acid/mole silver plus 2 g. formaldehyde/mole silver added.

was divided into The coatings were then processed exactly as described in Example 1 together with a duplicate set of coatings which had been previously incubated for one week at about 120 F. and 50% relative humidity.- The relative speed, contrast and fog for the coatings were then measured- The results are summarized in Table I.

TABLE 1."

Fresh Coating 1 Week Incubation at 120 F./b0% RH Exam 1e 2 Devolo er A 4 2% Developer A 4' No. A P D-u D-ll Rela- Con- Rola- Contlve trast Fog Fog ttve trast Fog Fog Speed 7 Speed EXAMPLE 3 A fine-grain, gelatino-silver-chlorobromide emulsion was sulfurand goldsensitized as-described in Example 1. This emulsion contained approximately 120 grams of gelatin per mole of silver halide. There were then added 2 grams of formaldehyde'per mole of silver halide and the emulsion was divided into s 'portions. Aldehydes were then added, at the concentration shown below, to four of the coatings. Thefifth coating served as a control and contained no aldehyde antifoggant. The emulsions were then coated on cellulose acetate supports and dried. -The coatings were exposed on an intensity scale sensitometer and processed in- Developer A of Example 1 for 2% minutes or in developer D-11 for four minutes. The coatings were then fixed,.washed and dried. Duplicate. coatings were processed after one weeks incubation at 120 F..and 50% relative humidity. The relative speed,.contrastgand fog were then measured. The results are shown in the following table:

TABLE II One week I incubation C t 4 Fresh coating :23 $20 113.] 0a rams lng Aldehyde Mole a No. .AgX

Rela- Con- D-11 Fog D-11 tive trast Fog Fog (Devel Fog Speed A) (8).... C0ntrol ..s 9.5 .01 .10 0.29 2. 46 (b).--. Muco- 1 107 10.5 .01 .02 .01 .10

ehloric acid. 50)-- Vanllltn..- 1 82 7.0 .01 .03 .01 .11 11)---. p -hy- 1 63 10.6 .01 .04 .01 .10

droxybenzulde- 11yde.. (0).- m-hy- 1 69 8.0 .01 .04 .01 .10

droxy- .benzaldehyde It has seen found that certain aldehydes, such as benzaldehyde, o-hydroxybenzaldehyde, succrmc dialdehyde,

rnaleic dialdehyde, etc. do not function as antifoggants 1n my invention. It is important in the case of aromatic aldchydcs that they contain a'substituent in either the 3- or 4-position .with respect to the aldehyde group.

The emulsions used in my invention can be either acidic or basic emulsions.

The photographic emulsions used in practicing my invention are of the developing-out type.

The-emulsions can also. be treated with salts of the noble metals such as ruthenium, rhodium, palladium,

- iridium, and platinum. 'Representative compounds are ammonium chloropalladate, potassium chloroplatinate,

and sodium chloropalladite, which are used for sensitizingin amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli U.S. Patent 2,448,060, issued August 31, 1948, and as antifoggants in higher amounts, as described in Trivelli and Smith U.S. Patents 2,566,245, issued August 28, 1951, and 2,566,263, issued August 28, 1951.

The emulsions can also be chemically sensitized with reducing agents such as stannous salts (Carroll U.S. Patent 2,487,850, issued November 15,1949), polyamines,

such as diethylene triamine (Lowe and; Jones U.S. Patent 2,518,698, issued August. 15, 1950), polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,925, issued September 12, 1950), or '-bis(fi-aminoethyl) sulfide and its water-soluble salts (Lowe and Jones U.S. Patent 2,521,926, issued September. 12, 1950).

The emulsions can also be optically sensitized with a pounds of the quaternary ammonium type of Carroll U.S. Patent 2,271,623, ,issued February 3, 1942; Carroll and Allen U.S. Patent: 2,288,226, issued June 30, 1942;

and Carroll andSpence U.S. Patent'2,334,864, issued November 23, 1943; andthe polyethylene glycol type of Carroll and "Beach U.S. Patent 2,708,162, issued May 10, 1955; or the thiopolymers of Graham and Sagal U.S. application Serial No. 779,839, filed December 12, 1958 (now U.S. Patent 3,046,129, issued July 24, 1962), or

Dann and Chechak U.S. application Serial No. 779,874, filed December 12, 1958 (HOW U.S. Patent 3,046,134,

issued'July 24, 1962), or thequaternary ammonium salts and polyethylene glycols of Piper U.S.-Patent 2,886,437, issued May 12, 1959. 15v

The emulsions may contam a suitable gelatin plasticizer such as glycerin; a dihydroxy alkane such .as 1,5- pentane diol as described in Milton and Murray U.S. application Serial No.- 588,951, filed June 4, 1956 (now U.S. Patent'2,960,404, issued November 16, 1960); an

ester of an ethylene bis glycolic acid such as ethylene bis(methyl glycolate) as described in Milton U.S. ap-

' plication Serial No. 662,564, filed May 31, 1957 (now U.S. Patent 2,904,434, issuedSeptember 15, 1959); bis- (ethoxy diethylene glycol) succinate as described in Gray US. application 'Serial No; 604,333, filed August 16,

' 1956 (now U.S. Patent 2,940,854, issued June 14, 1960),

cy'anine and merocyanine dyes, such as those described in'Brooker U.S. Patents 1,846,301, issued February 23, 1932; 1,846,302, issued February 23, 1932; and 1,942,

A. 854, issued January 9, 1934; White U.S. Patent 1,990,-

507, issued February 12, 1935; Brooke) and White U.S. Patents 2,112,140, issued March 22, 1938; 2,165,338, issued July 11, 1939; 2,493,747, issued January 10, 1950;

, and 2,739,964, issued March 27, 1956; Brooker and Keyes U.S. Patent 2,493,748, issued January 10, 1950; Sprague U.S. Patents 2,503,776, issued April 11, 1950, and 2,519,- 001, issued August 15,1950; Heseltine and Brooker U.S.

Patent 2,666,761, issued January '19, .1954; Heseltine" US, Patent 2,734,900 issued February 14', 1956; Van Lare U.S. Patent 2,739,149, issued March 20,1956; and Kodak Limited British Patent 450,958, accepted July 15, 1936.

The emulsions canalso be stabilized with the mercury compounds of Allen, Byers and Murray U.S. Patent 2,728,663, issued December 27, 1955; Carroll and Murray U.S. Patent 2,728,664, issued December 27, 1955; and Leubner and Murray US; Patent 2,728,665., issued December 27, 1955; the tri'azoles of Heimbach and Kelly U.S. Patent 2,444,608, issued July 6, 1948; the azaindenes of Heirnbach and Kelly U.S. Patents 2,444,605 and 2,444,606, issued July 6, 1948; Heimbach Patents 2,444,607, issuedJuly 6, 1948, and 2,450,397, issued 2 September 28, 1948; Heimbachand Clark U.S. Patent 2,444,609, issued July 6, 1948 Allen and Reynolds U.S. Patents 2,713,541, issued July 19, 1955, and 2,743,181,

. issued April 24, 1956; Carroll and Beach U.S. Patent 2,716,062,- issued August 23, 1955, Allen andfBeilfuss U.S. Patent 2,735,769, issued February 21, 1956; Roy'- nolds and Sagal U.S. Patent 2,756,147, issued July 24, 1956; Allen and Sagura U.S. Patent 2,772,164, issued November 27, 1956, and those disclosed by Birr in Z. wiss. Phot.,- vol. 47, 1952, pages 2-28; the disulfides of Kodak Belgian. Patent 569,317, issued July 31, 1958; the quaternary benzothiazolium compounds 'of Brooker and Staud US. Patent 2,131,038, issued September 27,

1938', or the polymethylene bis-benzothiazolium salts of Allen" and Wilson U.S. Patent 2,694,716, issued Novem-,

ber 16, 1954 (e'.g., decamethylene-bis-benzothiazolium perchlorate); or the zinc and cadmium salts of Jones US. Patent 2,839,405, issued June 17, 1958; and the carboxymethylmercapto compounds of Murray, Reynolds and Van Allan U.S. Patent 2,819,965, issued January The emulsions may also contain speed increasing comor a polymeric hydrosol as results from the emulsion polymerization of a mixture of an amide of an acid of the acrylic acid series, an acrylic acid ester and a styrene type compound as described in Tong'U.S. Patent 2,852,- 386, issued September 16, 1958. The plasticizer may be added to the emulsion before or after the addition of a sensitizing dye, if used.

The emulsions may contama coating aid such as saponin; a lauryl oroleyl'rnonoether of polyethylene glycol as described in Knox and Davis U.S. Patent 2,831,766, issued ,April 22, 1958; a salt of a sulfatedand alkylated polyethylene glycol ether as described in Knox and Davis U.S. Patent 2,719,087, issued September 27, 1955; an

acylated alkyl taurine such as the sodium salt of N-oleoyl- N-methyl taurine as described in Knox, Twardokus and Davis U.S.Patent 2,739,891, issued March 27, 1956; the

reaction product of adianhydride of tetracarboxybutane with an alcohol or an aliphatic amine containing from 8 to 18 carbon atoms which is treated with a base, for example, the sodium'salt of the monoester of tetracarboxybutane as described in Knox, Stenberg and Wilson U.S.

Patent 2,843,487, issued July 15, 1958, a water-soluble maleopimarate or a mixture of a water-soluble maleopimarate and a substituted glutamate salt as described in Knox and Fowler U.S. Patent 2,823,123, issued February 11, 1958; an alkali metal salt of a substituted amino acid such as disodium N -(carbo-p-tert. octylphenoxypentaethoxy)-glutamate* as described in Knox and Wilson U.S. patent application Serial No. 600,679, filed July 30, 1956 (now U.S. Patent 3,038,804, issued June 12, 1962); or" a sulfosuccinamate such as tetrasodium N-(1,2-dicarboxybeing useful in X-ray and other nonoptically sensitized emulsions, they may also be used in orthochromatic, pan

. chromatic, and infrared sensitive emulsions; They may be added to the emulsion before or after any sensitizing dyes which are used. Various silver salts may be used as the sensitive salt, such as silver bromide, silver iodide, silver chloride, or mixed silver halides such as silver chlorobromide or silverbromoiodide. The agents may be used in emulsions intended for color photography, for example, emulsions containing color-forming couplers or emulsions to be developed by solutions containing coupiers or other. color-generating materials, emulsions of the mixed-packet type, such as described in Godowsky U.S. Patent 2,698,794, issued January 4, 1955; or emulsions of the mixed-grain type, such as described in Carroll in diffusion transfer processes which utilize the undeveloped silver halide in the nonimage areas of the negative to form a positive by dissolving the undeveloped silver halide and precipitating it on a receiving layer in close 20 with. respect to the aldehyde group, said substituent beproximity to the original silver halide emulsion layer. Such processes are described in Rott U.S. Patent 2,352,- 014, issued June 20, 1944, and Land U.S. Patents 2,584, 029, issued January 29, 1952; 2,698,236, issued December 28, 1954, and' 2,543,181, issued February 27, 1951; and Yackel et al. U.S. patent application Serial No. 586,- 705, filed May 23, 1956 (now U.S. Patent 3,020,155, issued February- 6, 1962). They may also be used in color transfer processes which utilize the diffusion transfer of an image-wise distribution of developer, coupler or dye,

' from a light-sensitive layer to a second layer, while the two layers are in close proximity to one another. Color processes of this type are described in Land U.S. Patents 2,559,643, issued July 10, 1951, and 2,698,798, issued January 4, 1955;, Land and Rogers Belgian Patents 554,- 933 and 554,934, granted August 12, 1957; International Polaroid Belgian Patents 554,212, granted July 16, 1957,

. and 554,935, granted August 12, 1957; Yutzy U.S..Paten't 2,756,142, granted July 24, 1956, andWhitmore and Mader US. patent application Serial No. 734,141, filed May 9, 1958.

Inthe preparationofthe silver halide dispersions employed for preparing silver halideemulsions, there may be employed as the dispersing agent for the silver halide in itspreparation, gelatin or some other colloidal material such as colloidal albumin, a cellulose derivative, or a synthetic resin, for instance, a polyvinyl compound. Some colloids which may be used are polyvinyl alcohol or a hydrolyzed polyvinyl acetate as described in Lowe U.S.

Patent 2,286,215, issued June 16, 1942; a far hydrolyzed cellulose ester such as cellulose acetate hydrolyzed to an acetyl content of 19-26% as described in U.S. Patent 2,327,808 of Lowe and Clark, issued August 24, 1943;

a water-soluble ethanolamine cellulose acetate asde- I scribed in Yutzy U.S. Patent 2,322,085, issued June 15,

55 stabilized with mucochloric acid.

1943; 21 polyacrylamide having a combined acrylimide content of 15-20% and a specific viscosity of 0.09-0.225 or an imidized polyacrylarnide having a combined acrylimide content of 30-60%, a combined acrylic acid content'of 4-l2% and a specific viscosity of .251.5 as described in Lowe, Minsk and Kenyon US. Patent 2,541,- 60

474, issued February 13, 1951; zein as described in Lowe U.S. Patent 2,563,791, issued August 7, 1951; a vinyl alcohol polymer containing'urethane 'carboxylic acid groups of the type described in Unruh and .Smith U.S. Patent 2,768,154, issued October 23, 1956; or containing cyano-acetyl groups such as the vinyl alcohol-vinyl cyanoacetate copolymer as described in Unruh, Smith and Priest U.S. Patent 2,808,311, issued October 1, 1957; or.

a polymeric material which results from polymerizinga protein or a saturated acylated proteinwith a monomer having avinyl group as described in U.S. Patent 2,852,- 382, of Illingsworth, Dann and- Gates, issued September 16, 1958. t

If desired, compatible mixtures of two or more of these colloids may be employed fordispersing the silver halide will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

What I.claim as my invention and desire secured by Letters Patent of the United States is: a

1 .A photographic silver halideemulsion hardened substantially only with formaldehyde, sensitized with a labile sulfur compound and a gold salt, and stabilized with an aldehyde-compound selected from the class consisting of mucochloric acid, a water-soluble 'salt of mucochloric acid, mucobromic acid, a water soluble salt of mucobromic acid and'an aromatic aldehyde containing a substituent only in at least one of the positions: the 3-position with respect to the aldehyde group and the 4-position ing selected from the class consisting of an hydroxyl group, a halogen atom, a lower alkylgroup, and an alkox- 'yl group, said aro'matic aldehyde containing from 7 to 10 carbon atoms. I

2. A photographic element comprising a support and a photographic silver halide emulsion layer sensitized with a labile sulfur compound and a gold salt, and

stabilized by the addition of a compound selected from the class consisting of mucochloric acid, a water-soluble .30 salt of mucochloric acid, mucobromic acid, a watersoluble salt of mucobromic acid, and an aromatic aldehyde containing from 7 to 10 carbon atoms and containing a substituent only in at least one of the positions: the 3-position' with respect to the aldehyde group and the 4- position with respect to the aldehyde group, said substituent being selected from the class consisting of an hydroxyl group, a halogen atom, a lower alkyl group and an alkoxyl groupfand contiguous to said photographic silver halide emulsion layer a hydrophilic colloid layer, at least 40 one of said layers containing formaldehyde, said emulsion layer being hardened substantially only by said formaldehyde.

3. A photographic material according to claim 1 wherein the'photographic emulsion is a gelatino-silver halide photographic emulsion.

4. A photographic ge'latino-silver-halide emulsion hardened substantially only with formaldehyde, sensitized with a labile sulfur compound and a gold salt, and stabilized with an aldehyde compound selected from the class. consisting of p-hydroxybenzaldehyde, m-hydroxybenzaldehyde and vanillin.

5. A photographic gelatino-silver-halide emulsion hardened substantially only with formaldehyde, sensitized with a labile sulfur compound and a gold salt, and

6. A photographic gelatino-silverhalide emulsion .hardened substantially only withformaldehyde, sensitized 5 hardened substantially only with formaldehyde, sensitized with a labile sulfur compound and a gold salt, and stabilized with vanillin.

9. A photographic element comprising a photographic gelatino-silver-halide emulsion layersensitized with a labile sulfur compound and a gold salt and stabilized with an aromatic aldehyde selected from the class consisting of p hydroxybenzaldehyde, m hydroxybenzaldehyde and vanillin, and contiguous to said photographic silver halide emulsion layer a hydrophilic colloid layer, at least one of said layers containing formaldehyde, said emulsion layer being hardened substantially only by said formaldehyde.

' ing hardened substantially only by said formaldehyde.

' 11. A photographic element comprising a photographic v gelatino-silver-halide emulsion layer sensitized with a labile sulfur compound and a gold salt and stabilized with p-hydroirybenzaldehyde, and contiguous to said silver halide emulsionlayer a gelatin layer, at least one .of said layers containing formaldehyde, said emulsion layer being hardened substantially only bysaid formaldehyde.

12. A photographic element comprising a photographic gelatino-silver-halide emulsion layer sensitized with a labile sulfur compound and a gold salt and stabilized with m-'hydroxybenz aldehyde, and contiguous to said silver halide emulsion layer a gelatin layer, atleast one of said layers containing formaldehyde, said emulsion layer being hardened substantially only by said formaldehyde.

13. A photographic element comprising a photographic gelatino-silver-halide emulsion layer sensitized with a labile sulfur compound and a gold salt and stabilized 1 w-ith vanillin, and contiguous to saidsilver halide emulsion layera gelatin layer, at least oneof said layers containingformaldehyde, said emulsion layer being hardened substantially only by said formaldehyde.

References Cited in the file of this patent UNITED STATES PATENTS 2,165,421 Sheppard etal July 11, 1939 2,226,183 Stand et'al Dec. 24, 1940" 2,399,083 Waller et. a1 Apr.,23, 1946 2,591,542 Harriman Apr. 1, 1952 2,624,674 Tarkington Jan. 6, 1953 2,860,982 Jones NOV. 18, 1958 2,870,013 Jeffreys Jan; 20., 1959'- FOREIGN PATENTS 826,492

France Sept. 9, 1 937 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION HARDENED SUBSTANTIALLY ONLY WITH FORMALDEHYDE, SENSITIZED WITH A LABILE SULFUR COMPOUND AND A GOLD SALT, AND STABILIZED WITH AN ALDEHYDE COMPOUND SELECTED FROM THE CLASS CONSISTING OF MUCOCHLORIC ACID, A WATER-SOLUBLE SALT OF MUCOCHLORIC ACID, MUCOBROMIC ACID, A WATER SOLUBLE SALT OF MUCOBROMIC ACID AND AN AROMATIC ALDEHYDE CONTAINING A SUBSTITUENT ONLY IN AT LEAST ONE OF THE POSITIONS: THE 3-POSITION WITH RESPECT TO THE ALDEHYDE GROUP AND THE 4-POSITION WITH RESPECT TO THE ALDEHYDE GROUP, SAID SUBSTITUENT BEING SELECTED FROM THE CLASS CONSISTING OF AN HYDROXYL GROUP, A HALOGEN ATOM, A LOWER ALKYL GROUP, AND AN ALKOXYL GROUP, SAID AROMATIC ALDEHYDE CONTAINING FROM 7 TO 10 CARBON ATOMS. 